diff --git a/crawler.go b/crawler.go
index cbcb4d9..4c16f2f 100644
--- a/crawler.go
+++ b/crawler.go
@@ -144,7 +144,7 @@ func (c *Crawler) fetchCoverImg(code coverCode) error {
 	imgUrl := strings.ReplaceAll(c.config.GetString("crawler.url"), `*`, codeStr)
 	suffix := filepath.Ext(imgUrl)
 
-	fileName := filepath.Join(c.outputPath, fmt.Sprintf("%s-%d%s",
+	fileName := filepath.Join(c.outputPath, fmt.Sprintf("%s-%03d%s",
 		strings.ToUpper(code.letters),
 		code.number,
 		suffix,